Google has announced the acquisition of Sparrow, the developers of the highly popular e-mail client for Apple OS X and iOS, as the search giant (presumably) moves to revamp its approach to mobile Gmail.

“We care a lot about how people communicate, and we did our best to provide you with the most intuitive and pleasurable mailing experience. Now we’re joining the Gmail team to accomplish a bigger vision — one that we think we can better achieve with Google,” wrote Sparrow CEO Dom Leca in a blog entry announcing the acquisition.

Tat “bigger vision” probably means that Sparrow is at the very least expanding its reach beyond the Apple ecosystem – in light of today’s news, an Android version of Sparrow, or at least a Sparrow-powered Gmail mobile app, seems almost a given.

And speaking of the mobile app, Sparrow confirms that it’s going to be both offering and fully supporting the existing apps even as it merges into Google. Sparrow has earned praise for their streamlined, socially-integrated and extremely appealing interface (despite the common complaint that the iOS version still doesn’t support push messaging), and it’s definitely something the relatively staid Gmail apps could use. Of course, while Sparrow is still supporting these older versions, it’s not going to further develop them, either.

The Verge reports that Sparrow sold for under $25 million.

“The Sparrow team has always put their users first by focusing on building a seamlessly simple and intuitive interface for their email client. We look forward to bringing them aboard the Gmail team, where they’ll be working on new projects,” a Google spokesperson told 9to5 Mac.

There’s an interesting dichotomy in Google’s mobile strategy. Google likes to talk a big game about everything being in the cloud, and the browser being the ideal interface for combining productivity and portability. But at the same time, users are continually pressuring it to build out the offline components of its ecosystem, and the Android operating system itself is increasingly core to Google’s business.

As Microsoft tries to make online and mobile a more integral part of the Microsoft Office experience (perhaps with the wrong strategy), it’s almost funny that Google is trying to improve its native app play.

Either way, judging from the conversation on Twitter today, it seems obvious that if Google doesn’t do something major with the Sparrow technology, there are going to be a lot of disappointed ex-users.